Volume 49

Numerical Investigation into the Production Characteristics and Methane Leakage from the Hydrate Reservoir with Underlying Free Gas in Horizontal Well System Weiyu Yuan, Jing-Chun Feng, Bo Li, Tingting Zhang, Yan Xie, Bin Wang, Si Zhang, Zhifeng Yang

Abstract

This study established a Class I gas hydrate reservoir model (namely, a double-layer reservoir consisting of an upper hydrate-bearing layer and its underlying free gas water mixing layer) based on the hydrate exploration data from the Site GMGS4-SC_W02 in Shenhu area of South China Sea. Then a numerical simulation of hydrate extraction using the TOUGH+HYDRATE simulator was carried out. The gas-liquid production characteristics during hydrate exploitation using horizontal wells under different production schemes were analyzed. The production potential and the risk of methane leakage were evaluated. The results showed that the depressurization method is the optimal way for the low permeability Class I reservoirs exploitation in the view of long-term production. In addition, depressurization combined with thermal stimulation (in-situ wellbore heating) production did not show significant synergistic effects on increasing production and efficiency for Class I reservoirs. Instead, the pure thermal stimulation method can make a large amount of methane leak from the reservoir to the overburden layer, with the underlying free gas being the main source of methane leakage.

Keywords natural gas hydrate exploitation, horizontal well, methane leakage, free gas, numerical simulation